(57) A fiber-containing product based on seeds of legu­minous plants comprises the cell wall ingredients of the seed, said ingredients being isolated upon previous removal of the seed coat. The product is prepared by whole seeds of leguminous plants- being shelled to remove the cellulose-containing seed coat and being rinsed and steamed for bacterio­logical reasons - are wet-ground to open the plant cells and to dissolve or suspend the starch parti­cles, proteins, and soluble components contained in the plant cells; whereafter proteins, salts, soluble ingredients, and starch particles are re­moved as a filtrate through a filtration on a cen­trifugal sieve followed by a washing, filtration, and pressing of the resulting filter cake to in­crease the dry matter content before the filter cake is rasped and dried. The fiber product can be used when preparing e.g. an expanded and crisp product or for prophylactic or relieving treatment of human beings or animals, where the fiber-contain­ing product is administered in an effective prophy­lactic or relieving amount depending on the condi­tion being treated.